Known portable display devices have a center panel and two side panels hingedly connected thereto to form a display surface. Information, such as text, drawings, charts, photos and the like may be placed on the display surface and the portable display device may be stood up on a flat surface to present the information on a vertical display surface. The side panels are typically angled forwardly to form props that maintain the portable display device in its vertical display position. The side panels fold onto the center panel for storage and transport of the portable display device.
Such portable display devices are shown in U.S. Pat. No. 4,794,712, U.S. Pat. No. 5,293,705, and U.S. Pat. No. 5,911,522.
When standing, the side panels of such a portable display device provide good support against tipping over in the forward direction. However, the portable display devices of this type are typically unsupported against tipping over backwards, relying on the weight of the forwardly angled side panels to prevent such backward tipping. People walking bristly past such an upright display device can create enough air current to turn it over, as can air currents from fans, open doors, or the like. Accidentally touching or pushing the portable display device can tip it over, as can leaning anything against it.
Therefore, it would be a great improvement to provide a portable display device that supports itself against backward tipping.